This proposal is designed to compare the tumor cell kinetics of the original colorectal tumor with the cell kinetics of the early transplants of the tumor into "nude" mice. The purpose of the project is to determine if the nude mouse model is an adequate one in which to test appropriate chemotherapeutic drugs and their different schedules. The cell kinetic measurements will be done in vitro and consist of 3HTdR LI, DNA synthesis time, and PDP (growth fraction) assay. Additionally, the glucocortico-steroid receptors of colorectal tumors will be determined and correlated with the tumor cell kinetics.